1. Field of the Invention
The present invention relates generally to high-energy-density capacitors, materials for high-energy-density capacitors, and methods of making high-energy-density capacitors.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Dielectric materials play a key role in modern electronics and electric-power systems, e.g., due to their use in capacitors and batteries. An important characteristic of a dielectric material is its dielectric strength, defined as the maximum electric-field strength that the material can withstand without breaking down, e.g., through a catastrophic failure of its electrical insulating properties. For a representative dielectric material, the maximum energy density (UD) that can be stored in the material is given by Eq. (1):
                              U          D                =                              1            2                    ⁢                      ɛ            d                    ⁢                      ɛ            0                    ⁢                      E            B            2                                              (        1        )            where ∈d is the dielectric constant of the material; ∈0 is the dielectric permittivity of free space; and EB is the dielectric strength. It is beneficial to have access to high energy-storage densities, e.g., because the use of the corresponding dielectric materials in energy-storage devices enables a significant reduction in the volume, weight, and cost of those devices.
Eq. (1) indicates that both the dielectric constant and dielectric strength of the material are important for achieving high (e.g., greater than about 10 J/cm3) energy-storage densities. However, these energy-storage densities are not yet supported by the dielectric materials that are commercially available today. For example, metal oxides have relatively large dielectric constants but relatively low dielectric strengths. Organic materials (e.g., polymers) can have relatively high dielectric strengths, but are usually characterized by modest-to-low dielectric constants.